Chemically Modified Variants of Fenofibrate with Antiglioblastoma Potential.

Anticancer effects of a common lipid-lowering drug, fenofibrate, have been described in the literature for a quite some time; however, fenofibrate has not been used as a direct anticancer therapy. We have previously reported that fenofibrate in its unprocessed form (ester) accumulates in the mitochondria, inhibits mitochondrial respiration, and triggers a severe energy deficit and extensive glioblastoma cell death. However, fenofibrate does not cross the blood brain barrier and is quickly processed by blood and tissue esterases to form the PPARα agonist fenofibric acid, which is practically ineffective effective in triggering cancer cell death. To address these issues, we have made several chemical modifications in fenofibrate structure to increase its stability, water solubility, tissue penetration, and ultimately anticancer potential. Our data show that, in comparison to fenofibrate, four new compounds designated here as PP1, PP2, PP3, and PP4 have improved anticancer activity in vitro. Like fenofibrate, the compounds block mitochondrial respiration and trigger massive glioblastoma cell death in vitro. In addition, one of the lead compounds, PP1, has improved water solubility and is significantly more stable when exposed to human blood in comparison to fenofibrate. Importantly, mice bearing large intracranial glioblastoma tumors demonstrated extensive areas of tumor cell death within the tumor mass following oral administration of PP1, and the treated mice did not show any major signs of distress, and accumulated PP1 at therapeutically relevant concentrations in several tissues, including brain and intracranial tumors.

Spatially graded hydrogels for preclinical testing of glioblastoma anticancer therapeutics.

While preclinical models such as orthotopic tumors generated in mice from patient-derived specimens are widely used to predict sensitivity or therapeutic interventions for cancer, such xenografts can be slow, require extensive infrastructure, and can make in situ assessment difficult. Such concerns are heightened in highly aggressive cancers, such as glioblastoma (GBM), that display genetic diversity and short mean survival. Biomimetic biomaterial technologies offer an approach to create ex vivo models that reflect biophysical features of the tumor microenvironment (TME). We describe a microfluidic templating approach to generate spatially graded hydrogels containing patient-derived GBM cells to explore drug efficacy and resistance mechanisms.

Alisertib demonstrates significant antitumor activity in bevacizumab resistant, patient derived orthotopic models of glioblastoma.

Aurora A kinase (AURKA), a member of the serine/threonine kinase family, plays a critical role in cell division, and it is widely overexpressed in a variety of tumors including glioblastoma (GBM). Alisertib (MLN8237) is an orally administered selective AURKA inhibitor with potent antiproliferative activity, currently undergoing clinical testing in different tumor types. In vitro evaluation of alisertib against the primary GBM lines, GBM6, GBM10, GBM12 and GBM39 showed significant antitumor activity with IC50s ranging between 30 and 95 nM. Orthotopic xenografts of GBM10 and the bevacizumab resistant lines GBM6 and GBM39 were established by implantating 3 × 105 cells in the caudate nucleus of nude mice; animals were randomized to treatment with either alisertib 30 mg/kg/day or vehicle. In all three models, treatment with alisertib resulted in a statistically significant prolongation of survival (p < 0.0001). In addition, alisertib administration in these mice decreased phosphorylated aurora-A, induced mitotic arrest and significantly decreased histone H3 phosphorylation in tumors. In conclusion, alisertib displays significant antitumor activity against primary GBM lines and xenografts, including patient derived GBM lines resistant to bevacizumab; these data support clinical translation in GBM.

Improving drug delivery to primary and metastatic brain tumors: strategies to overcome the blood-brain barrier.

Brain tumor diagnosis has an extremely poor prognosis, due in part to the blood-brain barrier (BBB) that prevents both early diagnosis and effective drug delivery. The infiltrative nature of primary brain tumors and the presence of micro-metastases lead to tumor cells that reside behind an intact BBB. Recent genomic technologies have identified many genetic mutations present in glioma and other central nervous system (CNS) tumors, and this information has been instrumental in guiding the development of molecularly targeted therapies. However, the majority of these agents are unable to penetrate an intact BBB, leading to one mechanism by which the invasive brain tumor cells effectively escape treatment. The diagnosis and treatment of a brain tumor remains a serious challenge and new therapeutic agents that either penetrate the BBB or disrupt mechanisms that limit brain penetration, such as endothelial efflux transporters or tight junctions, are required in order to improve patient outcomes in this devastating disease.

EGFRvIII stimulates glioma growth and invasion through PKA-dependent serine phosphorylation of Dock180.

Glioblastomas (GBMs), the most common and malignant brain tumors, are highly resistant to current therapies. The failure of targeted therapies against aberrantly activated oncogenic signaling, such as that of the EGFR-PI3K/Akt pathway, underscores the urgent need to understand alternative downstream pathways and to identify new molecular targets for the development of more effective treatments for gliomas. Here, we report that EGFRvIII (ΔEGFR/de2-7EGFR), a constitutively active EGFR mutant that is frequently co-overexpressed with EGFR in clinical GBM tumors, promotes glioma growth and invasion through protein kinase A (PKA)-dependent phosphorylation of Dock180, a bipartite guanine nucleotide exchange factor (GEF) for Rac1. We demonstrate that EGFRvIII induces serine phosphorylation of Dock180, stimulates Rac1 activation and glioma cell migration. Treatments of glioma cells using the PKA inhibitors H-89 and KT5720, overexpression of a PKA inhibitor (PKI), and in vitro PKA kinase assays show that EGFRvIII induction of serine phosphorylation of Dock180 is PKA-dependent. Significantly, PKA induces phosphorylation of Dock180 at amino acid residue S1250 that resides within its Rac1-activating DHR-2 domain. Expression of the Dock180(S1250L) mutant, but not wild type Dock180(WT), protein in EGFRvIII-expressing glioma cells inhibited receptor-stimulated cell proliferation, survival, migration in vitro and glioma tumor growth and invasion in vivo. Together, our findings describe a novel mechanism by which EGFRvIII drives glioma tumorigenesis and invasion through PKA-dependent phosphorylation of Dock180, thereby suggesting that targeting EGFRvIII-PKA-Dock180-Rac1 signaling axis could provide a novel pathway to develop potential therapeutic strategies for malignant gliomas.

Oncolytic measles virus strains have significant antitumor activity against glioma stem cells.

Glioblastoma (GBM) is the most common primary brain tumor in adults and has a dismal prognosis despite multimodality treatment. Given the resistance of glioma stem cells (GSC) to chemotherapy and radiation therapy, their eradication could prevent tumor recurrence. We sought to evaluate the antitumor activity of measles virus (MV) derivatives against GSC. We generated neurosphere cultures from patient-derived primary tumor GBM xenografts, and we characterized them for the GSC markers CD133, SOX2, Nestin, ATF5 and OLIG2. Using the MV-strains MV-GFP, MV-CEA and MV-NIS we demonstrated infection, viral replication and significant cytopathic effect in vitro against GSC lines. In tumorigenicity experiments, GBM44 GSC were infected with MV in vitro and subsequently implanted into the right caudate nucleus of nude mice: significant prolongation of survival in mice implanted with infected GSC was observed, compared with mock-infected controls (P=0.0483). In therapy experiments in GBM6 and GBM12 GSC xenograft models, there was significant prolongation of survival in MV-GFP-treated animals compared with inactivated virus-treated controls (GBM6 P=0.0021, GBM12 P=0.0416). Abundant syncytia and viral replication was demonstrated in tumors of MV-treated mice. Measles virus derivatives have significant antitumor activity against glioma-derived stem cells in vitro and in vivo.

p53 isoform profiling in glioblastoma and injured brain.

The tumor suppressor p53 has been found to be the most commonly mutated gene in human cancers; however, the frequency of p53 mutations varies from 10 to 70% across different cancer types. This variability can partly be explained by inactivating mechanisms aside from direct genomic polymorphisms. The p53 gene encodes 12 isoforms, some of which can modulate full-length p53 activity in cancer. In this study, we characterized p53 isoform expression patterns in glioblastoma, gliosis, non-tumor brain and neural progenitor cells by SDS-PAGE, immunoblot, mass spectrometry and reverse transcription-PCR. We found that the most consistently expressed isoform in glioblastoma, Δ40p53, was uniquely expressed in regenerative processes, such as those involving neural progenitor cells and gliosis compared with tumor samples. Isoform profiling of glioblastoma tissues revealed the presence of both Δ40p53 and full-length p53, neither of which were detected in non-tumor cerebral cortex. Upon xenograft propagation of tumors, p53 levels increased. The variability of overall p53 expression and relative levels of isoforms suggest fluctuations in subpopulations of cells with greater or lesser capacity for proliferation, which can change as the tumor evolves under different growth conditions.

Identification and evaluation of a potent novel ATR inhibitor, NU6027, in breast and ovarian cancer cell lines.

BACKGROUND: The ataxia telangiectasia mutated and Rad3-related kinase (ATR) has a key role in the signalling of stalled replication forks and DNA damage to cell cycle checkpoints and DNA repair. It has long been recognised as an important target for cancer therapy but inhibitors have proved elusive. As NU6027, originally developed as a CDK2 inhibitor, potentiated cisplatin in a CDK2-independent manner we postulated that it may inhibit ATR. METHODS: Cellular ATR kinase activity was determined by CHK1 phosphorylation in human fibroblasts with inducible dominant-negative ATR-kinase dead expression and human breast cancer MCF7 cells. Cell cycle effects and chemo- and radiopotentiation by NU6027 were determined in MCF7 cells and the role of mismatch repair and p53 was determined in isogenically matched ovarian cancer A2780 cells. RESULTS: NU6027 is a potent inhibitor of cellular ATR activity (IC(50)=6.7 µM) and enhanced hydroxyurea and cisplatin cytotoxicity in an ATR-dependent manner. NU6027 attenuated G2/M arrest following DNA damage, inhibited RAD51 focus formation and increased the cytotoxicity of the major classes of DNA-damaging anticancer cytotoxic therapy but not the antimitotic, paclitaxel. In A2780 cells sensitisation to cisplatin was greatest in cells with functional p53 and mismatch repair (MMR) and sensitisation to temozolomide was greatest in p53 mutant cells with functional MMR. Importantly, NU6027 was synthetically lethal when DNA single-strand break repair is impaired either through poly(ADP-ribose) polymerase (PARP) inhibition or defects in XRCC1. CONCLUSION: NU6027 inhibits ATR, impairing G2/M arrest and homologous recombination thus increasing sensitivity to DNA-damaging agents and PARP inhibitors. It provides proof of concept data for clinical development of ATR inhibitors.

ATM as a target for novel radiosensitizers.

DNA damage checkpoints are complex signal transduction pathways that are critical for normal cellular recovery following potentially lethal genotoxic insults. The ataxia-telangiectasia mutated (ATM) protein kinase is a critical component in these pathways and integrates the cellular response to damage by phosphorylating key proteins involved in cell cycle regulation and DNA repair. Lack of normal ATM function in the inherited ataxia-telangiectasia (A-T) syndrome results in a pleiotropic clinical syndrome characterized by a marked increased risk of cancer and profound hypersensitivity to ionizing radiation. Cells derived from patients with A-T share some of these attributes with genomic instability, loss of normal cell cycle arrest pathways, defects in DNA repair and increased radiation sensitivity. The radiosensitivity of A-T cells suggests that pharmacological inhibitors of the ATM kinase should be effective radiosensitizing agents. In fact, caffeine inhibits ATM kinase activity at concentrations that result in an A-T-like phenotype with loss of cell cycle checkpoints and hypersensitivity to ionizing radiation. Although the clinical use of caffeine as a radiosensitizer is limited by potentially lethal systemic toxicities, more potent methyl xanthines may selectively inhibit the ATM pathway at clinically achievable levels. Interestingly, caffeine and other methyl xanthines preferentially radiosensitize cells that lack normal p53 function. Because p53 is commonly inactivated in epithelial malignancies, this suggests that small molecule inhibitors of ATM might selectively sensitize the majority of tumors to the lethal effects of ionizing radiation while sparing normal tissues.

The radiosensitizing agent 7-hydroxystaurosporine (UCN-01) inhibits the DNA damage checkpoint kinase hChk1.

The investigational anticancer agent 7-hydroxystaurosporine (UCN-01) abrogates the G2 checkpoint in tumor cells and sensitizes them to the lethal effects of genotoxic anticancer agents. On the basis of the role of the Cdc25C phosphatase in maintenance of this damage-inducible checkpoint, we hypothesized that UCN-01 inhibits a component of the signal transduction pathway that modulates Cdc25C phosphorylation. Of the three kinases known to phosphorylate Cdc25C on Ser216, both checkpoint kinase 1 (hChk1) and Cdc25C-associated protein kinase 1 (cTAK1) were potently inhibited by UCN-01 with IC50s of 11 and 27 nM, respectively. Treatment of K562 erythroblastoid leukemia cells with similar drug concentrations resulted in decreased levels of Ser216 phosphorylation of Cdc25C and complete disruption of the y-radiation-induced G2 checkpoint. In contrast to hChk1, the hChk2 kinase was 100-fold more resistant to inhibition by UCN-01 (IC50, 1040 nM). These results suggest that disruption of the DNA damage-induced G2 checkpoint by UCN-01 is mediated through the inhibition of the Cdc25C kinases, hChk1 and cTAK1, and that hChk2 activity is not sufficient to enforce the G2 checkpoint in cells treated with a pharmacological inhibitor of hChk1.

High-dose-rate versus low-dose-rate brachytherapy in the treatment of cervical cancer: analysis of tumor recurrence--the University of Wisconsin experience.

PURPOSE: To retrospectively compare the clinical outcome for cervical cancer patients treated with high-dose-rate (HDR) vs. low-dose-rate (LDR) brachytherapy. METHODS AND MATERIALS: One hundred ninety-one LDR patients were treated from 1977 to 1988 and compared to 173 HDR patients treated from 1989 to 1996. Patients of similar stage and tumor volumes were treated with identical external beam fractionation schedules. Brachytherapy was given in either 1 or 2 LDR implants for the earlier patient cohort, and 5 HDR implants for the latter cohort. For both patient groups, Point A received a minimum total dose of 80 Gy. The linear-quadratic formula was used to calculate the LDR dose-equivalent contribution to Point A for the HDR treatments. The primary endpoints assessed were survival, pelvic control, relapse-free survival, and distant metastases. Endpoints were estimated using the Kaplan-Meier method. Comparisons between treatment groups were performed using the log-rank test and Cox proportional hazards models. RESULTS: The median follow-up was 65 months (2 to 208 months) in the LDR group and 22 months (1 to 85 months) in the HDR group. For all stages combined there was no difference in survival, pelvic control, relapse-free survival, or distant metastases between LDR and HDR patients. For Stage IB and II HDR patients, the pelvic control rates were 85% and 80% with survival rates of 86% and 65% at 3 years, respectively. In the LDR group, Stage IB and II patients had 91% and 78% pelvic control rates, with 82% and 58% survival rates at 3 years, respectively. No difference was seen in survival or pelvic control for bulky Stage I and II patients combined (>5 cm). Pelvic control at 3 years was 44% (HDR) versus 75% (LDR) for Stage IIIB patients (p = 0.002). This difference in pelvic control was associated with a lower survival rate in the Stage IIIB HDR versus LDR population (33% versus 58%, p = 0.004). The only major difference, with regard to patient characteristics, between the Stage IIIB patients was the incidence of hydronephrosis in the HDR vs. LDR group--28% vs. 12%, respectively (p = 0.05). For Stage IIIB patients treated with HDR, our analysis suggested that pelvic control rates improved when the first brachytherapy insertion was performed after the majority of external beam radiotherapy had been delivered. CONCLUSION: Similar outcome was observed for Stage IB and II patients treated with either HDR or LDR brachytherapy-regardless of tumor volume. However, poorer survival and pelvic control rates were observed for Stage IIIB patients treated with HDR brachytherapy. If HDR is used for Stage IIIB patients, our results suggest the majority of external beam radiotherapy should be delivered prior to initiating the brachytherapy to allow for adequate tumor regression. HDR brachytherapy is more convenient for patients, decreases the radiation exposure for health care workers, and should be considered a standard therapy for women with Stage I or II cervical cancer.

Inhibition of ATM and ATR kinase activities by the radiosensitizing agent, caffeine.

Caffeine exposure sensitizes tumor cells to ionizing radiation and other genotoxic agents. The radiosensitizing effects of caffeine are associated with the disruption of multiple DNA damage-responsive cell cycle checkpoints. The similarity of these checkpoint defects to those seen in ataxia-telangiectasia (A-T) suggested that caffeine might inhibit one or more components in an A-T mutated (ATM)-dependent checkpoint pathway in DNA-damaged cells. We now show that caffeine inhibits the catalytic activity of both ATM and the related kinase, ATM and Rad3-related (ATR), at drug concentrations similar to those that induce radiosensitization. Moreover, like ATM-deficient cells, caffeine-treated A549 lung carcinoma cells irradiated in G2 fail to arrest progression into mitosis, and S-phase-irradiated cells exhibit radioresistant DNA synthesis. Similar concentrations of caffeine also inhibit gamma- and UV radiation-induced phosphorylation of p53 on Ser15, a modification that may be directly mediated by the ATM and ATR kinases. DNA-dependent protein kinase, another ATM-related protein involved in DNA damage repair, was resistant to the inhibitory effects of caffeine. Likewise, the catalytic activity of the G2 checkpoint kinase, hChk1, was only marginally suppressed by caffeine but was inhibited potently by the structurally distinct radiosensitizer, UCN-01. These data suggest that the radiosensitizing effects of caffeine are related to inhibition of the protein kinase activities of ATM and ATR and that both proteins are relevant targets for the development of novel anticancer agents.

A role for ATR in the DNA damage-induced phosphorylation of p53.

Phosphorylation at Ser-15 may be a critical event in the up-regulation and functional activation of p53 during cellular stress. In this report we provide evidence that the ATM-Rad3-related protein ATR regulates phosphorylation of Ser-15 in DNA-damaged cells. Overexpression of catalytically inactive ATR (ATRki) in human fibroblasts inhibited Ser-15 phosphorylation in response to gamma-irradiation and UV light. In gamma-irradiated cells, ATRki expression selectively interfered with late-phase Ser-15 phosphorylation, whereas ATRki blocked UV-induced Ser-15 phosphorylation in a time-independent manner. ATR phosphorylated p53 at Ser-15 and Ser-37 in vitro, suggesting that p53 is a target for phosphorylation by ATR in DNA-damaged cells.

Perioperative morbidity and mortality of high-dose-rate gynecologic brachytherapy.

PURPOSE: To determine the 30-day morbidity and mortality rates for patients with an intact uterus undergoing high-dose-rate (HDR) brachytherapy, and to assess risk factors which may predict for these potentially life-threatening complications. METHODS AND MATERIALS: From August 1989 to December 1994, 128 cervical and 41 medically inoperable endometrial cancer patients were treated with 5 outpatient weekly HDR brachytherapy insertions. Patients with cervical cancer also were treated with external beam radiotherapy. Acute events that resulted in either hospitalization (morbidity) or death (mortality) within 30 days of the implant were analyzed. Univariate and multivariate analyses were performed to identify risk factors. RESULTS: Overall there were 16 acute events in 169 patients (9.5%). The overall morbidity and mortality rates for the cervical and endometrial patients were 5.5%, 1.6%, 7.3%, and 9.8%, respectively. The following factors were significant by univariate analysis: age per decade, American Society of Anesthesiologists (ASA) score, Karnofsky Performance Status (KPS), significant medical history, diagnosis of cervical vs. endometrial cancer, and mean time exceeding 160 minutes for the procedure. Since age was the most significant predictive factor (p = 0.0003), bivariate analyses were performed by adjusting for age. In these analyses only ASA and KPS maintained significance, while a positive medical history was of borderline significance (p = 0.07). CONCLUSION: The morbidity and mortality rates observed in gynecologic patients selected for HDR brachytherapy were similar to low-dose-rate, but higher than other HDR reports. Reasons for this include a higher risk population, especially those with medically inoperable endometrial cancer. In the cervical cancer patients, some of the complications may have also been a result of the external beam portion of the radiation. In order to minimize the acute complications observed in the present HDR brachytherapy system, the following changes have been implemented: appropriate patient selection, anesthesiology involvement to monitor conscious sedation for high-risk patients, external beam radiotherapy alone in patients at extremely high risk, deep vein thrombosis (DVT) prophylaxis, use of intraoperative ultrasound, shorter duration in the brachytherapy suite, and preradiation treatment plans (plans executed prior to the insertion) if applicable. Finally, this analysis suggests that these procedures should be performed in a hospital-based setting where appropriate support is available.

Inhibition of phosphoinositide 3-kinase related kinases by the radiosensitizing agent wortmannin.

Members of the phosphatidylinositol-3 kinase related kinase (PIKK) family function in both cell cycle progression and DNA damage-induced cell cycle checkpoints. The fungal metabolite, wortmannin, is an effective radiosensitizer that irreversibly inhibits certain members of the PIKK family. Based on their roles in DNA damage responses, several PIKKs, DNA-dependent protein kinase (DNA-PK), ataxia telangiectasia mutated (ATM) and the ataxia- and Rad3-related protein (ATR), are potential targets for the radiosensitizing effect of wortmannin. In this report, we demonstrate that wortmannin is a relatively potent inhibitor of DNA-PK (IC50, 16 nM) and ATM (IC50, 150 nM) activities, whereas ATR activity is significantly less sensitive to this drug (IC50, 1.8 microM). In intact A549 lung adenocarcinoma cells, wortmannin inhibited both DNA-PK and ATM at concentrations that correlated closely with those required for radiosensitization. Furthermore, pretreatment of A549 cells with wortmannin resulted in radioresistant DNA synthesis, a characteristic abnormality of ATM-deficient cells. These results identify wortmannin as an inhibitor of ATM activity and suggest that ATM and DNA-PK are relevant targets for the radiosensitizing effect of this drug in cancer cells.

Comparison between pulsed-field gel electrophoresis and the comet assay as predictive assays for radiosensitivity in fibroblasts.

The radiosensitivity of skin fibroblasts derived from patients as measured in vitro by a clonogenic survival assay appears to correlate with the risk of developing severe late reactions to radiation. Unfortunately, these assays are clinically impractical as a predictive test for radiosensitivity. The purpose of this study was to assess the utility of two possible surrogate assays for radiosensitivity, pulsed-field gel electrophoresis (PFGE) and single-cell gel electrophoresis (comet assay), both of which can be used to measure DNA double-strand breaks. Twenty-three nontransformed human fibroblast cell lines exhibiting a range of radiosensitivities were studied with both of these assays. The results were correlated with measurements of radiosensitivity obtained as part of a larger study examining the correlation between cellular radiosensitivity and clinical response. [2-(14)C]Thymidine-labeled confluent cultures were irradiated at 1.0 Gy/min with doses of 0 to 150 Gy. After allowing 4 h for repair at 37 degrees C, cells were trypsinized and aliquots were used for preparing slides for the comet assay. After neutral lysis and electrophoresis, the slides were stained with ethidium bromide and 50 comet moments were measured for each dose. The remainder of the cells were formed into agarose plugs and, after neutral lysis, were subjected to PFGE. The fraction of activity released (FAR) from the well was measured by scintillation counting of appropriate segments of each gel lane. Cellular radiosensitivity was measured with a standard clonogenic assay at a low dose rate of 1.2 cGy/min, and the dose that resulted in a surviving fraction of 0.01 (D0.01) was calculated. The slope of the plot of comet moment as a function of dose for each cell line did not correlate with D0.01 (R = 0.36, P > 0.1). In contrast, the slope of the FAR as a function of dose had a weak inverse correlation with D0.01 (R = 0.43 and P = 0.05) such that the more radiosensitive cell lines exhibited a steeper dose response for FAR. Although the correlation between the slope of the dose response for FAR and D0.01 was weak, refinement of the PFGE technique may provide a potentially useful predictive assay for radiosensitivity.

Radiosurgery in the initial management of malignant gliomas: survival comparison with the RTOG recursive partitioning analysis. Radiation Therapy Oncology Group.

PURPOSE: To evaluate the impact of stereotactic radiosurgery on the survival of patients treated with malignant gliomas. METHODS AND MATERIALS: A total of 115 patients from three institutions (75 from the Joint Center for Radiation Therapy, 30 from the University of Wisconsin, and 10 from the University of Florida) were treated with a combination of surgery, external beam radiation therapy, and linac-based radiosurgery as part of similar institutional protocols from March 1988 through July 1993. Patients were stratified into six prognostic classes (classes 1-6) based on the recursive partitioning analysis of multiple prognostic factors previously reported by the Radiation Therapy Oncology Group. RESULTS: The actuarial 2-year and median survival for all patients analyzed was 45% and 96 weeks, respectively. In comparison to the results from a previously published analysis of 1578 patients entered on three Radiation Therapy Oncology Group external beam radiotherapy protocols from 1974 to 1989, those patients treated with radiosurgery had a significantly improved 2-year and median survival (p = 0.01) corresponding with a standardized mortality risk ratio of 0.51 [95% confidence interval (CI): 0.31, 0.85]. This improvement in survival was seen predominantly for the worse prognostic classes (classes 3-6). The 2-year survival for the radiosurgical patients compared with the previously reported patients was 81% vs. 76% for classes 1/2, 75% vs. 35% for class 3, 34% vs. 15% for class 4, and 21% vs. 6% for classes 5/6, respectively. Although Karnofsky performance status and prognostic class were significant on univariate analysis, only the Karnofsky score was a significant predictor of outcome on multivariate analysis. Median and 2-year survival for patients with a Karnofsky score > or = 70 was 106 weeks and 51%, respectively, as compared to 38 weeks and 0% for patients with a Karnofsky score < 70% (p = 0.001). CONCLUSIONS: The addition of radiosurgery to conventional treatment (surgery and external beam radiotherapy) of malignant gliomas appears to improve survival when compared to historical reports. These results should be interpreted with caution because the recursive partitioning model does not completely predict the prognosis of the patients treated in the present study. Although this study suggests that radiosurgery may prolong survival in patients with malignant gliomas, the role of radiosurgery in the management of these patients remains to be defined by a prospective randomized trial.

The adverse effect of treatment prolongation in cervical carcinoma.

PURPOSE: Proliferation of surviving tumor clonogens during a course of protracted radiation therapy may be a cause of local failure in cervical carcinoma. The effect of total treatment time was analyzed retrospectively in relation to pelvic control and overall survival for squamous cell carcinomas of the uterine cervix. METHODS AND MATERIALS: Two hundred and nine patients (Stage IB-IIIB) treated with a combination of external beam and low dose rate intracavitary irradiation were evaluable for study. Multivariate analysis and Kaplan-Meier statistical methods were used to determine the effect of treatment time on pelvic control and survival at 5 years. RESULTS: The median treatment duration was 55 days. For all stages combined, the 5-year survival and pelvic control rates were significantly different with treatment times < 55 days vs. > or = 55 days: 65 and 54% (p = 0.03), 87 and 72% (p = 0.006), respectively. By stage, a shorter treatment duration (i.e., < 55 days vs. > or = 55 days) was significant for 5-year overall survival and pelvic control for Stages IB/IIA and III, but not for Stage IIB: Stage IB/IIA (81 and 67%, 96 and 84%), Stage III disease (52 and 42%, 76 and 55%) and Stage IIB (43 and 50%, 74 and 80%, respectively). Survival decreased 0.6%/day and pelvic control decreased 0.7%/day for each additional day of treatment beyond 55 days for all stages of disease. Additionally, significant late complications were not influenced by treatment time. CONCLUSION: These results suggest that prolongation of treatment time is associated with decreased local control and survival in patients with cervical carcinoma. This is consistent with emerging data from other institutions. Therapeutic implications include avoidance of unnecessary treatment breaks, the design of fractionation schemes that decrease treatment duration, and possibly the use of tumor cytostatic drugs during conventional radiation.

The decreased influence of overall treatment time on the response of human breast tumor xenografts following prolongation of the potential doubling time (Tpot).

PURPOSE: Repopulation during fractionated radiotherapy has been postulated to result in a significant loss in local control in rapidly proliferating tumors. Clinical data suggest that accelerated fractionation schedules can overcome the influence of repopulation by limiting the overall treatment time. Unfortunately, accelerated therapy frequently leads to increased acute reactions, which may become dose limiting. An alternative to accelerated fractionation would be to decrease the rate of repopulation during therapy. To test the potential efficacy of this alternative, we examined the effect of reducing tumor proliferation rate on the response of MCF-7 human breast carcinoma xenografts treated with a short vs. a long course of fractionated therapy. To reduce the proliferation rate, we deprived nude mice transplanted with MCF-7 xenografts of the growth-stimulating hormone estradiol (E2). We have previously reported that E2 deprivation increases the potential doubling time (Tpot) for MCF-7 xenografts from a mean of 2.6 days to 5.3 days (p < 0.001). METHODS AND MATERIALS: E2-stimulated and E2-deprived MCF-7 breast carcinoma xenografts were clamped hypoxically and irradiated with four fractions of 5 Gy each, using either a short (3-day) or long (9-day) treatment course. E2 stimulation was restored in all animals at the completion of irradiation. Radiation response was determined by regrowth time and regrowth delay of the irradiated tumors as compared to unirradiated controls. RESULTS: Prolongation of therapy in rapidly proliferating, E2-stimulated tumors (Tpot approximately 2.6 days) resulted in a significant decrease in regrowth time in two identical experiments. With results pooled for analysis, the regrowth times for the short and long treatments were 62 and 32 days, respectively (combined p < 0.001). The shorter regrowth times suggest that there was less overall tumor damage with the longer fractionated radiotherapy course. No significant difference in regrowth time was observed in the more slowly proliferating, E2-deprived tumors (Tpot approximately 5.3 days) treated with either the short or long regimen. Median regrowth times were 48 and 54.5 days for the short and long treatments, respectively (combined p = 0.14). Similar changes were observed in regrowth delay. CONCLUSIONS: Reduction in the rate of cell proliferation, induced by E2 deprivation in MCF-7 human breast xenografts during fractionated radiotherapy, resulted in a significantly decreased dependence on overall treatment time in comparison to the more rapidly proliferating E2-stimulated tumors. This model suggests that pharmacologically induced reduction in the rate of tumor cell proliferation during a course of fractionated radiotherapy may be a viable alternative to accelerated fractionation for the treatment of rapidly proliferating tumors.

A comparison of the efficacy and complication rates of low dose-rate versus high dose-rate brachytherapy in the treatment of uterine cervical carcinoma.

PURPOSE: To compare the outcome and complication rates for treatment of uterine cervical carcinoma with low dose-rate (LDR) vs. high dose-rate (HDR) brachytherapy at the University of Wisconsin Comprehensive Cancer Center (UWCCC). METHODS AND MATERIALS: One-hundred ninety-eight evaluable patients with cervical carcinoma, Stages IB to IIIB, treated with curative intent with a combination of megavoltage teletherapy and LDR brachytherapy from 1977 to 1988 were the subject of an initial review. In 1989, a HDR treatment program was initiated where all patients with cervical carcinoma were subsequently treated with a combination of HDR brachytherapy and teletherapy. Using the linear-quadratic model (LQ), the dose and schedule of HDR brachytherapy and teletherapy were designed to give similar tumor control and late effects as LDR therapy. Technically, the HDR schedule required meticulous attention to treatment geometry to limit severe late effects. Forty patients treated with the HDR program with 2-4 year follow-up were reviewed and compared to the previous LDR patient group. The LDR and HDR treatment groups were comparable with regards to age, weight, stage distribution, bulk of disease, and histology. RESULTS: No significant difference in survival was found between the LDR and HDR groups with 3-year actuarial overall survival being 66% and 77%, respectively. Three-year actuarial pelvic control rates were similar at 80% and 77% for the LDR and HDR groups, respectively. No significant difference in late treatment complications requiring hospitalization or surgery was found between the two treatment groups with a complication rate of 10% (20/198) for the LDR patients and 2.5% (1/40) for the HDR patients. CONCLUSION: As predicted by our LQ calculations, treatment results for LDR and HDR brachytherapy were similar with respect to survival, pelvic control and late complications in the treatment of cervical carcinoma. The HDR brachytherapy program at the UWCCC appears to be a safe and effective alternative to LDR therapy in the treatment of cervical carcinoma.